MAGELLAN STATUS REPORT May 25, 1993 8:30 PM PDT The Magellan spacecraft started its Transition Experiment this morning at 10:31 AM PDT with an Orbit Trim Maneuver which lowered its periapsis (closest approach to Venus) to 149.4 km. Telemetry indicated that the 11.3 minute burn of the thrusters was normal, and the resulting periapsis altitude was 149.7 km. Following the first atmospheric drag pass, all subsystems were reported to be nominal. Temperatures of the solar panels increased by about 7 to 9 degrees C as a result of atmospheric friction. This is about half the expected value. The attitude control system generated about 2800 thruster pulses as the control shifted from reaction wheel control to thrusters and back during the pass. Much of this activity is caused by the residual momentum from the wheels being transferred to the body of the craft. Power and Telecom were nominal. Nearly identical telemetry measurements were received following the next two drag passes (Orbits 7628, 7629). During the next four days a series of walk-in trim maneuvers will further lower the periapsis until the spacecraft is in the desired corridor. Based on the present navigation and spacecraft data, the next two OTMs (Orbit Trim Maneuvers) will be the "double down" magnitude. The first of the corridor -adjustment OTMs is scheduled for 5:46 AM PDT tomorrow. Ron Baalke Jet Propulsion Lab Pasadena, CA 91109 MAGELLAN STATUS REPORT May 27, 1993 3:00 PM PDT The Magellan Transition Experimet continues as the flight team carefully maneuvers the spacecraft toward the desired aerobraking corridor. The second "double down" trim maneuver was performed at 2:07 PM PDT today to lower the periapsis to 143 km. At the Mission Director meeting early this afternoon, a "single down" OTM was approved for execution on Saturday. This will lower the periapsis by 1.6 km. All spacecraft subsystems continue to report nominal performance. There have been some difficulties with transfer of 1200 bps telemetry between JPL and Denver. On the incident of orbit 7638 last night, Attitude Control estimates that the spacecraft performed the drag pass about 120 deg.off the proper attitude. Spacecraft systems responded as designed and there was no damage to the craft. The solar panels were facing the sun and stayed near 85 degrees C.(instead of cooling to 25 and then warming to 39 during the drag pass). Attitude control stayed in phase plane D, and used about 0.046 kg of fuel during the pass. From orbit 7639 on the spacecraft performance has been normal. Ron Baalke Jet Propulsion Lab Pasadena, CA 91109 MAGELLAN STATUS REPORT May 27, 1993 10:00 AM PDT The Magellan Transition Experiment continues as the flight team carefully maneuvers the spacecraft toward the desired aerobraking corridor. The spacecraft has now made fifteen atmospheric drag passes with periapsis below 150 km and all subsystems were reported to be nominal. As the spacecraft approaches the low part of the orbit, the attitude control system switches from reaction wheel control to the thrusters. Depending on the amount of attitude error when this switch occurs, the thrusters have used from 0.013 to 0.023 kg of fuel to maintain the position within 10! of the velocity vector. The expected fuel consumption is 0 to 0.3 kg per orbit. Shortly before orbit 7638 last night, an update to the periapsis time table was sent to Magellan. An error in the coded data was rejected by the on-board computer, and the spacecraft apparently went through the atmospheric drag pass in the wrong attitude. Spacecraft systems responded as designed and there was no damage to the craft. The solar panels were facing the sun and stayed near 60 degrees C.(instead of cooling to 25 and then warming to 39 during the drag pass). Attitude control stayed in phase plane D, and used about 0.046 kg of fuel during the pass. From orbit 7639 on the spacecraft performance has been normal. Based on the present navigation and spacecraft data, the next OTM (Orbit Trim Maneuver) will be the "double down" magnitude. The second of the corridor-adjustment OTMs is scheduled for 2:07 PM PDT today. Ron Baalke Jet Propulsion Lab Pasadena, CA 91109 PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011 PLANETARY MISSION STATUS May 27, 1993 GALILEO: The spacecraft is now en route to Jupiter, scheduled to enter orbit December 7, 1995. Spacecraft performance and condition are excellent except that the high-gain antenna is only partly deployed; science and engineering data are being transmitted via the low-gain antenna. The mission team is planning to use the low-gain antenna for the Jupiter mission and for the encounter August 28, 1993 with asteroid Ida. Galileo was launched October 18, 1989, flew by Venus in 1990 and Earth in 1990 and 1992 for gravity assists, and flew by asteroid Gaspra in October 1991 for scientific observation. Contact: Jim Wilson, (818) 354-5011. MAGELLAN: The Magellan spacecraft has concluded its eight-month survey of the gravitational field of Venus from its elliptical orbit. On May 25, flight controllers began an 80-day program to lower and circularize the spacecraft's orbit by aerobraking, dipping into Venus's upper atmosphere each orbit. Magellan was launched May 4, 1989 and radar-mapped more than 98 percent of Venus's surface from September 1990 to September 1992. Contact: Jim Doyle, (818) 354-5011. MARS OBSERVER: Spacecraft health and performance are normal, after several episodes in which it entered contingency mode, a safe state triggered by the spacecraft computer because of attitude-reference anomalies. A software fix has solved the problem. Mars Observer is scheduled to enter Mars orbit August 24, 1993; it will be moved into a mapping orbit by November 8 and science operations are planned to start November 22. Mars Observer was launched September 25, 1992. Contact: Diane Ainsworth, (818) 354-5011. TOPEX/POSEIDON: The satellite is healthy, and all scientific instruments are performing normally, typically providing three playbacks per day. The mission is mapping ocean circulation. TOPEX/Poseidon was launched August 10, 1992. Contact: Mary Hardin, (818) 354-5011. ULYSSES: The spacecraft is in a highly inclined solar orbit now 31.7 degrees south relative to the Sun's equator, in transit from its Jupiter gravity assist in February 1992 toward its solar polar passages (about 80 degrees south and north) in 1994 and 1995. Spacecraft condition and performance are excellent, with Ulysses gathering data on the heliosphere -- the realm dominated by the solar wind, a stream of charged particles flowing from the Sun. The Ulysses spacecraft was built by the European Space Agency and launched October 6, 1990. Contact: Diane Ainsworth, (818) 354-5011. VOYAGER 1 and 2: The two Voyager spacecraft have detected low-frequency radio emissions believed to originate at the boundary between the solar wind and the interstellar medium, called the heliopause. Detection and measurement of this boundary is the principal goal of the Voyager Interstellar Mission. Voyager 1, launched September 5, 1977, is currently 7.8 billion kilometers (4.8 billion miles) from the Sun after flying by Jupiter and Saturn in 1979 and 1980; Voyager 2, launched August 20, 1977, to fly by Jupiter (1979), Saturn (1981), Uranus (1986) and Neptune (1989), is now 6 billion kilometers (3.7 billion miles) from the Sun. Contact: Mary Hardin, (818) 354-5011. Ron Baalke Jet Propulsion Lab Pasadena, CA 91109 VOYAGER HELIOPAUSE DIAGRAM May 28, 1993 A GIF image of the Voyager heliopause diagram is now available at the JPL Info public access site. Note that the image is in GIF89a format, so make sure your display software supports this format (as opposed to the older GIF87a format). The image is available by dialup modem at +1 (818) 354-1333, up to 9600 bps, parameters N-8-1 (will be moved to the images directory in 30 days) file: vgrhelio.gif Ron Baalke Jet Propulsion Lab Pasadena, CA 91109